1. Field of the Invention
The subject disclosure relates to leak detectors, and more particularly to leak detectors for backflow prevention devices in water systems.
2. Background of the Related Art
Generally, backflow is any unwanted reversal of the flow of liquids, solids, or gases in a piping system such as a fire protection system. For another example, backflow in an irrigation application is when water from the sprinkler system travels “upstream” through the pipes and enters the potable water system through a cross-connection. A cross-connection is any connection between a potable (drinkable) water system and any system containing non-potable water, pollutants, or toxins. An example of where a cross-connection would exist is when a home's external tap has a hose connected that runs into a pool, which is elevated above the home's water tank.
Backpressure can also create undesirable contamination. Backpressure is when the pressure downstream of the backflow devices exceeds the supply (or upstream) pressure. Backpressure can occur if the supply pressure is reduced, or if the pressure downstream is increased. Back siphonage can also create contamination. Back siphonage occurs when a vacuum is created upstream of the backflow device, and water is literally sucked back up the system. Back siphonage can happen when the water supply is stopped due to a water main break or nearby fire hydrant use.
In view of the above, many types of backflow prevention devices have been designed to prevent contaminants from entering potable water systems. Backflow prevention devices are used in all types of premises, whether industrial, commercial or residential. Backflow prevention devices help protect the public safety by preventing potable water contamination in such critical areas as municipal water systems, food processing plants, medical and dental water supplies, and many industrial applications. The Safe Drinking Water Act, signed into law in 1974, placed the responsibility of local governments and water authorities for drinking water protection to promote public health and safety. As a result, most building codes and prudent designers require backflow prevention devices.
There are multiple types of backflow prevention devices or back flow preventers, the three most common being the pressure vacuum breaker (PVB), the reduced pressure zone (RPZ), and the double check assembly (DCA). These are all installed in the water system immediately after the isolation valve. There is a fourth backflow preventer which is also fairly common; the atmospheric vacuum breaker (AVB), which is installed on each zone of the sprinkler system, immediately after the zone control valve. Each type of backflow device is designed to provide a different level of protection for varying commercial or residential applications. For example, hospitals and morgues, which handle large quantities of hazardous wastes on a daily basis, require much heavier-duty backflow preventers than a residential irrigation system. Several backflow prevention devices are available at watts.com/backflowprevention.
One phenomenon of some backflow prevention devices is the occasional ejection of some water or even the release of a significant amount of water. For example, a pressure fluctuation where a building pressure rises above the main pressure may cause momentary backflow that is released by the backflow prevention device. In another more dramatic circumstance, the main pressure drop may be sustained, which could result in the water within a building being dumped to drain to prevent backflow contamination. For a tall building, this could be a significant amount of water at a large flow rate.
To accommodate water released from backflow prevention devices, systems are usually designed so that the released water goes to drain. However, the drain system may be insufficient, blocked or even non-existent. Often, the drain system has an inlet funnel for catching the released water. Such inlet funnels usually maintain an air gap to the water system, again for preventing cross-connection and, thereby, a potential source of contamination.